3-D structured cell systems. Microbeam experiments RARAF is also a user facility for biologists interested in performing microbeam studies. The prominent theme of research undertaken using the RARAF microbeam is damage signal transduction, both within cells and between cells, which is of interest due in part to the discovery of the radiation-induced bystander effect. Early inter-cellular signal transduction studies were done with cells plated in 2D monolayers. More recently due to the significance of the extracellular environment and technological developments, studies involving 3D tissue systems,<ref name="Sedelnikova07">Sedelnikova OA et al. DNA double-strand breaks form in bystander cells after microbeam irradiation of three-dimensional human tissue models. '"Cancer Res. 67:4295-302 (2007).</ref> including living organisms, have become more common. Applications of Microfluidics RARAF is developing various microfluidic devices which add to the irradiation capabilities of the facility. The precision control and manipulation of fluids and biological materials afforded by microfluidics are ideal to interface with the microbeam. Additional microfluidic systems beyond those listed here are currently under development. Flow and Shoot The Flow and Shoot microbeam system allows for controlled transport of cells through a microfluidic channel which intersects with the point and shoot microbeam. A high speed camera allows for dynamic targeting of the flowing cells with flow rates of 1–10 mm/s, allowing for total throughput upwards of 100,000 cells per hour. Optofluidic Cell Manipulation An optoelectronic tweezer platform has been interfaced with the RARAF microbeam. This allows precision manipulation of cell position before, during, and after irradiation. Caenorhabditis elegans immobilization RARAF has implemented a microfluidic platform for the immobilization of Caenorhabditis elegans during microbeam irradiation. The device avoids the use of anesthetics that might interfere with normal physiological processes by capturing the C. elegans worms in tapered microfluidic channels. It is possible to target specific regions of interest within C. elegans using this technology. Other Technologies Broad beam irradiations are also possible. Particles with linear energy transfer (LET) between 10 and 200 keV/μm are available utilizing beams of protons, deuterons, helium-3, and helium-4 ions. Additionally, energetic and thermal neutrons and x rays can be used in broad beam irradiations. Training Scientists RARAF has trained scientists at all levels: high school students, undergraduates, graduate students, post docs, and senior scientists. The lab estimates that about 45 scientists have received training in microbeam physics and or biology in the past 5 years. RARAF is an active participant in the Columbia University Research Experience for